I love my Fitech, have it controlling timing too, the driveability and hot/cold running, not to mention fuel economy, on my big cam car is incredible. But for a near stock car? I suspect the advantages are less, so it comes down to how much you want the fuel injection. There is definitely more install effort and ongoing troubleshooting, fixing, and general effort to keep the fuel injection working well. For me it is worth it, but if you just want something to get in and drive and never worry about, it would be hard to go past a good carb and HEI. Depends on your milage too, I average around 15,000 street and track miles each year in my Corvette.

 

Yea I was wondering about this, my car had an Edelbrock performer 2101 intake manifold on it. I also have done more research about this issue and most people who have installed this system (on 50's and 60's bel airs etc) say they have problems with the Holley efi on a dual plane intake but they put a half-inch to a 1 inch spacer on the intake before re-installing and they saw better results.

 

I should have said - I run mine on an Edelbrock Performer Rpm (so dual plane) with no problems whatsoever, but I have heard of a small number of people who do find it a problem. I would have bought a single plane but I already had the Performer Rpm an figured it was worth trying before shelling out money for a new manifold.

 

I have the Holley Sniper EFI in my '72 LeMans and I love it. It's replaced a Q-Jet built by Cliff. The Sniper starts right away (I don't have to crank it to wait for the fuel to fill the bowls), idles well, doesn't stall when the a/c kicks in and I love being able to monitor things with the display screen. I went with an EFI fuel tank and in-tank fuel pump. For the return line, instead of running a 3/8 inch line all the way from the throttle body to the tank, I installed this filter regulator just in front of the tank and had a very short return line. It works great. I also installed a 1/2" 4-hole spacer to lessen the whistle from the throttle body and an adjustable progressive secondary rod. Holley just announced the Hyperspark distributor for the Pontiac, so I ordered that today as well, in order to have the Sniper control timing.




I intend to install one in the Corvette, taking everything I learned from the install in my Pontiac and applying it to the '71 convertible. Using that filter regulator saved a ton of time, so I will do that again so I don't have to route a new return line the length of the car. I'm not sure I have the clearance for a spacer, but an L88 hood would solve that problem.

 

Thats a good point. For the carb, it think I figured out how to adjust the idle mixture and idle speed screws on it, ill try that and see what happens. Ive done some more research after my original post and I'm most likely going to keep my carb and just try and fine tune it. The carb was rebuilt last year, (Along with a new HEI Distributor, I had one in there that needed replacing) but it ever since it was rebuilt, the carb idle speed is just 400 RPM when in park, neutral, AND in drive, and is very sluggish in all the RPM ranges.

 

I run a Holley 8500c - Quad replacement on one C3 - runs excellent with great performance.

My other I run a Edelbrock which also runs great. No issues. Weiand manifold.

My other is a Q jet and it runs great - no issues.

The only issue I have with the fuel injection is: what happens when something goes wrong on a trip. With a carb I can walk into AutoZone and get one for $300 and be running in 20 minutes...

 

I hope it was the right rebuilder. There are quite a few that butcher the Q-Jet so it doesn't work right at all and some go so far they basically trash the carb,

 

Thank you for that advice, when this carb was rebuilt, I had a new HEI distributor installed along with ignition timing adjustments. I think ill
take a look at the timing and stuff too along with the carb.

 

EFI has its advantages in better idle speed control , maybe a little MPG, but does not ever make more power than a good carb .. I have a Quickfuel 750 SS DP on my stroker.. I dialed it in over 10 years ago on a dyno , and have not touched it since.. runs flawlessly . I see no need for the expense of EFI...................... and only FITech says theirs can auto-tune on an engine with 6-7 inches vacuum.. all the rest say no way . Just my 2 cents

 

Wow, was afraid of this.....will be staying with a carb. See a # of guys having to fool with their EFI or keep a touchscreen wired in to mess with makes no sense to me at all.

Sure the EFI has its perks but unless it was 100% factory new car reliable why bother? An electric FP will fill the bowls quick for cars that sit.
Thanks for posting you saved me thousands

 

Never worry about is misleading. I see lots of posts about carb issues here...

 

Just drove 600 miles to Carlisle, around the area, and back with my 71 and Edelbrock carb. No issues and 24.8 mpg.

 

I normally drive 600 miles in every 2 week period. To elaborate on my comment a bit more - I don't have a lot of problems, but maybe once every 2-3 months I'll chase down a minor issue, generally not anything that leaves me stranded though. I dunno, I guess with the amount I drive my car it would be almost no issues for most peoples usage. But I have driven carburettored cars for years without touching them - admittedly more standard cars, whereas my Corvette is pretty heavily modified, and that could be the difference.

 

Sounds like a good idea, but once he tweaks it, how long will it last until it gets out of tune again?

 

Hi, you mention "...more install effort and ongoing troubleshooting, fixing, and general effort to keep the fuel injection working well." I thought one of the strong points of EFI was that it did not need constant adjusting, like most EFI cars in the market nowadays... Can you elaborate.. Thanks!

 

X2 on having lars rebuild your q jet! Also, keep your points distributor and have it rebuilt and recurved to Lars specs on his ignition papers.

 

Fueling
To start with, any carb you can throw at the car should work with the stock fuel system. An EFI system will require at a minimum an electric pump put somewhere in the supply line. Your problems start here.

I went full-tilt on the fuel system, with an Aeromotive Phantom setup and two brand new AN-6 lines, a good regulator and filter setup. This guaranteed I wouldn't see pump starvation issues in hard acceleration (throttle, brake, steer) and with a return style system mitigates the risk of vapor lock.

The easiest system to setup would be an electric fuel pump tapped inline with the existing supply line, dead-headed with the carb. Vapor lock is more probable with a PWM, and the factory line may not handle the higher demands of fuel injection (higher pressure, more vibration).

Oxygen sensor(s)
The oxygen sensor needs to be installed far enough from a junction point to get a good average of cylinders and there can not be any upstream exhaust leaks or nearby downstream exhaust leaks. These will skew the mixture and cause the ECM to run in circles attempting to figure out what's going on.

Vacuum Leaks
Not as big a deal as exhaust leaks, but a vacuum leak will cause the model the ECM uses to figure out your projected fueling needs to be less predictable.

Some Tuning Required
Yes, EFI can compensate for a lot, but it won't know everything about your car and you'll need to help it along the way. You'll need to give it information about your camshaft, information about your desired timing curve, etc so that it can build a close enough model to base its assumptions on.

USE COMPUTER CONTROLLED SPARK!!
This is a HUGE one for me. The EFI ECM is designed to control combustion. Yes, it's called "Electronic Fuel Injection", but every system worth its salt is also going to have timing control capabilities. USE THEM, or stick with a carburetor. I'm serious. The carburetor's metering capabilities are capable of "good enough" to get you down the road, but the EFI is capable of getting things perfect - and it can control transient throttle conditions and idle much better with timing than it can controlling via fuel mixtures and IAC alone. If your ECM wants to throttle down the motor a bit, it's much easier for it to do that via spark than by playing with IAC.

I ran my car with the MSD Atomic EFI and the HEI distributor for maybe a month before investing in a full computer controlled timing setup. Night and day. The A/C system kickup, which included exciting one of the electric fans was more predictable, the car was less prone to stalling, and leaning into the gas pedal was much smoother. Absolutely worth it.

I do enjoy my EFI system. I would probably skip past TBI and go straight to a multiport, sequential system if I could. I like port injection - better fuel economy, better part throttle, plus the center-mount throttle bodies have just a little less stack height vs a carb or TBI unit if you're trying to sneak a larger intake under a Corvette hood.

Hope that helps.

 

This started out as an older thread. But many have added to it just recently. I'll throw in my 2 cents worth. I've run 2 different carbs. A quadrajet and a Holley on my Vette. Changing it over to EFI a little over a year ago now. I did it right. In tank pump with a baffle, all homemade setup. New lines front to back. But then after over 40 years, I thought it was due for new fuel lines anyway.
can't begin to compare the difference in overall driveability. Soooo, much nicer with EFI. starts, runs, at every RPM so much smoother, cleaner with EFI. No I don't drive around with a screen lit up all the time. What nonsense! I don't do that with my late model car or motorcycle!
But once I did. As I wanted to compare the temp readings through the ECU against the guage in my center guage cluster. While I was at it I also ran the AFR's on the screen just for giggles. Yes I learned my cars temp guage reads high. And was amazed at how the ECU kept the AFR's adjusted near perfect all the time.
with both carbs, when it sat for more than a day, it never, not once started on the first crank. Always took a second cranking to get it to fire. Never got the choke just right on either carb. Shut off to late, or to early. Never just right. EFI. Turn the key and go. Idles up for 30 seconds cold. Settles down and good for the day. Yes a bit of monkeying around in the beginning getting the map set up to my cam, compression, etc. But really just pushing buttons. Spent more time playing with fan start and shut off timing than anything. Only to learn my guage isn't accurate. If my EFI system does fail one day. By then they'll have something better I reckon. As per running into a Autoparts store and just grabbing a carburetor if one is on a road trip. Yah, cars haven't run carbs in HOW LONG! Not that many shops still stocking a selection of carburetors anymore. More likely to find an IAC or IAT.

 

I started out with a bunch of diffrent carbs. Different edelbrocks, then Qjets and I was super happy with my last one, an Edelbrock 1901 I believe. It was a 750 and I had tuned it with the help of Cliff Ruggles book. It was awesome and I got 18 mpg with it, my MSD dizzy, 6AL box, and my 5 speed at 80 - 85 mph. I found a great deal on a Holley Sniper
so I thought I would give it a shot since it was my end goal anyway. I plan on multiple cross country trips in the future and crossing the great divide will require it if I want it to perform well at altitude. I got it installed and it fired right up. The only issues I've really had was from me messing with it trying to tune it before it was done learning. Once I stopped monkeying with it the gas mileage started going up. I used the Holley in tank pump/ regulator and sender. Its plumbed to the original 3/8 line and the 1/4 inch return isnt attached yet. I do plan on hooking it up as a back up, just waiting on braided hose ends. At close to 500 hp the 3/8 is holding its own. No starvation problems. If I do notice them I'll just run braided line the whole length.

Now im messing with my gas gauge. Im giving this a shot

Classic Instruments Fuel Link Interface Modules SN34

https://www.summitracing.com/parts/CIN-SN34

 

The other side of the coin.
My 69 had a 434 SBC with a spread bore Holley with the choke removed. 2 pumps to start, a little feathering, then off we go. Started to have idle surging problems that were getting worse and after going through the carb twice I decided that come off season it would get a Holley Sniper along with a new tank from Tanks inc, with the built in fuel pump, new lines, etc. Now the fun begins. The first summer there was dying out problems that were finally diagnosed as excessive RFI [ ever try contacting Holley service] and resolving the problem by putting tin foil around the wiring and using the OEM chrome shielding that problem is finally corrected. Next the engine races up to 1800 rpm when restarting after being shut off 5 minutes earlier. Now it is surging again, but this time it is a failing injector, you can see that but cannot fix it. Or can you? I have a spare Quick fuel carb sitting in a box that is just begging to be put on, my off season project and it won't cost me 2 grand. Anybody want to buy a slightly used Holley Sniper? T